Hotels, office buildings and the like require door locks on a large number of individual rooms. In a hotel, for example, the door lock of each guest room should have a different key for successive guests. Also, at a given time, a guest room door lock must be operable by different keys assigned to hotel personnel, such as the maid, housekeeper and other levels of hotel management. For security purposes, the keys for each lock must be readily changeable.
In the prior art, locking systems for hotels and the like have been developed which utilize electronic code responsive logic circuits for operation of a lock mechanism.
The Aydin U.S. Pat. No. 4,177,657 granted Dec. 11, 1979 discloses an electronic lock system which senses code on a key and compares it to a code stored in a memory. When the key code matches the stored code, the lock activates a clutch operated bolt and may also change the stored code to a new code. The Aydin patent discloses a microcomputer control system for the lock. Each key has a control code, a primary key code and a secondary key code stored thereon. A read/write memory stores a predetermined number of assigned key codes and a read-only memory has a control program stored therein for control of the microcomputer. A key reader is coupled with the microcomputer and is adapted to coact with any of the keys to read the code stored thereon into the microcomputer. Different keys are used for different access levels in accordance with the control code on the key. The access levels are designated as guest key, floor master, section master, security master, etc. If a code match is obtained, the system performs two major functions, namely, enabling the clutch to permit door opening and changing of the stored code in the memory. In addition, there are certain auxiliary functions, namely, inhibiting opening to permit the change of code, a special key which can be used once only and a double lock function.
The Sabsay U.S. Pat. No. 3,821,704 discloses an electronic locking system suitable for hotels and the like and having multiple levels of master keys. Each lock mechanism is controlled by a decoding circuit having a changeable binary memory. A key has two decodable information fields, namely, a key field and an authorization field. When the key field matches the combination stored in the decoding circuit memory the lock opens. If there is not a match, the authorization field and the combination field are compared and if they are equal the key field is stored in the memory and the lock is opened.
The Dimitriadis U.S. Pat. No. 3,797,936 discloses an electronic lock which is provided with an optically encoded key. If the code on the key corresponds to the stored code, the circuit activates a mechanism which opens the lock. The Astin U.S. Pat. No. 4,396,914 discloses a microprocessor controlled lock. In this system an electronic circuit compares the content of the memory with the combination code and enables the lock device if a match is found. If the key card is a new one the circuit calculates a new combination code and if it matches that on the key card the memory is loaded with the new combination code.
A general object of this invention is to provide an improved security device which is especially adapted for use in controlling a door lock mechanism and which overcomes certain disadvantages of the prior art.